<table border="1" class="dataframe">
  <thead>
    <tr>
      <th colspan="2" halign="left">a</th>
      <th colspan="2" halign="left">b</th>
    </tr>
    <tr>
      <th>c</th>
      <th>d</th>
      <th>c</th>
      <th>d</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>0</td>
      <td>3</td>
      <td>5</td>
      <td>3</td>
    </tr>
    <tr>
      <td>1</td>
      <td>4</td>
      <td>6</td>
      <td>4</td>
    </tr>
  </tbody>
</table>
